intalling heat pump in place of central AC and making 11 year old oil fire furnace my back-up

oakland

I want to convert from oil fired hot air Lennox elite series furnace to a two stage variable speed Goodman heat pump and make my oil furnace the back-up. The Goodman heat pump will go in place of my 5 ton central AC unit and act as a heat and AC source. The furnace blower handled the AC and furnace hot air. I believe i can change the blower from single stage to variable speed with a retrofit motor. Do i have to change the old control board on the furnace because i am adding a second heat source and making the oil the back-up and trying to mesh two different companies and sharing the blower and making the blower variable speed?